Recently, the PET examination has attracted attention as an examination method for cancer, encephalopathy, and cardiopathy. In the PET examination, a radiopharmaceutical (referred to as a PET medicine) using nuclides emitting positrons (positive electron) as markers is dosed into the body of a subject, wherein gamma rays emitted outside the body, caused by the PET medicine accumulated at the diseased part or the PET medicine flowing through veins of the brain and the heart, are detected with a plurality of radiation detectors. The information obtained on the basis of the gamma ray detection signals outputted by these radiation detectors is used to provide tomographic images of the subject. Using the tomographic images, diagnosis of the blood flow or the like is carried out.
The PET examination is useful as an examination with a relative low load on patients in addition to the fact that it can find a cancer, for example, having a size equal to or less than 1 cm, which is difficult to be found by examinations with the CT (Computer Tomography, X-ray tomography) apparatus or the MRI (Magnetic Resonance Imaging, nuclear magnetic resonance tomographic imaging) apparatus and the fact that it provides the examination over the whole body of the subject in a shorter interval than that of the conventional examinations.
It is generally known that radioisotopes used in such PET examinations have short half-lives. As the radioisotopes, oxygen 15 (15O) having a half-life of about two minutes and fluorine 18 (18F) having a half-life of about two hours or the like exist. Particularly, the usefulness of 18F rapidly increases because of the relative long half-life as this type of a nuclide.
18F is produced generally by using a nuclear reaction generated by irradiating oxygen 18 (18O) with protons having high energy. 18O is an isotope of the oxygen 16 (16O) and naturally exists only by about 0.2%. Thus, it may be also considered to condense 18O to increase the yield. In fact, 18F is produced by irradiating a container filled with water containing 18O (H218O) with protons accelerated to about 10 MeV. Conventionally, to produce it, the cyclotrons which require relative large facilities are mainly used. Further, a technology for obtaining radioisotopes by irradiation with helium ions by a linear accelerator was also proposed (for example, WO9010937 discloses such a technology at page 9, line 25 to page 17, line 23).
In the general conventional production of 18F mentioned above, upon irradiating oxygen 18 (18O) with protons having high energy, a nuclear reaction generates rays (neutrons or the like). Thus, in the facilities accommodating the radioisotope production apparatus including an accelerator, it is important to shield against rays. Conventionally, to shield rays, there is a known method, in which thick walls comprising concrete as base members (radiation shield walls) are arranged integrally with the building (a ceiling and a floor) of the facilities around the room in which an accelerator or the like is installed.
However, there is a problem that it takes a long time to arrange thick walls for radiation shielding with much labor, and as well as the building itself should be made strong, so that the cost will increase. Further, there is also a problem that in the existent facility, the location of the radioisotope production apparatus is limited.
Further, as described above, since the half-lives of radioisotopes are relatively short, it is desirable to execute the process from synthesizing of the PET medicine to the PET examination in a short interval, and thus, the medical facilities having such a function have been desired.